Electric circuit interrupter



July 15, 1941. .1. w. SEAMAN ELECTRIC CIRCUIT INTERRUI TER Inven r. \Toap V\/.Se nfina is Att ney Patented July 15, 1941 UNITED STATES PATENTOFFICE ELECTRIC CIRCUIT INTERRUPTEB Joseph W. Seaman, Upper Darby, Pa.,assignor to General Electric Company, a corporation of New YorkApplication December 2, 1938, Serial No. 243,587

Claims. (Cl. 200-144) My invention relates to electric circuitinterrupters, more particularly to air circuit interrupters of the typewherein the arc is to be interrupted within confining or partiallyconfining means, such as an arc chute, and has for its principal objectthe provision in an air circuit interrupter of the character abovedeiined of improved arc-interrupting means that is effective rapidly toextinguish a high voltage power are within a comparatively small space,and to confine under all operating conditions the are within this space.

The use in arc chutes of arc cooling and quenching structures, such asmetal or insulating plates, between which the arc is driven, and spacedmetal pins or bars positioned transversely of the arc path is known inthe air circuit breaker art. In a well-known form, a circuit breaker ofthe magnetic blow-out type is provided with a plurality of spaced metalplates within an arc chute arranged so that the arc, as it is driveninto the plates by the blow-out field, is divided into a plurality ofserially related sections.

It has also been proposed to use in the arc chute spaced metal pins orbars for the purpose of cooling and quenching the arc. The designfactors, however, have not been clearly understood, particularly withrespect to the spacing and arrangement of the arc-quenching elements,with the result that are interruption has not been reasonably consistentexcept in the case of spacious arc chutes having a large aggregate massof cooling material.

I have found that in the case of spaced metal elements, such as pins orbars, there is an optimum for the relative spacing of these elementswithin the arc chute, regardless of both the aggregate mass of coolingmetal within the chute and the magnitude of the current to beinterrupted. This optimum spacing results in a compact and efilcient arcchute for a given interrupting rating. Specifically, I have found thatpins composed of a suitable non-magnetic metal, such as copper forexample, positioned transversely of the arc path between the insulatingwalls of an arc chute aremost eifective for are interruption when spacedapproximately from each other, the spacing being between adjacent pinarcing surfaces as contrasted with pin centers. A tolerance of plus orminus is within the scope of my invention, although the fa" spacing ispreferred. I

I have also found that an arc chute provided with arc-extinguishingstructure of the charatcer above described can also be made even moreeffective and compact by the use of an insulating arc baiile structureat the exhaust end of the chute. The baille structure is made up ofbaille plates spaced so as to form a plurality of approximately parallelnarrow slots each approximately V." in width extending substantiallyparallel to the arc path. These slots are effective not only as an aidin extinguishing the arc in case it is driven through the main arcextinguishing means, but also to prevent extension of the arc exteriorlyof the chute. The slots however provide free venting of the arc gaseswithin the chute.

My invention will be more fully set forth in the following descriptionreferring to the accompanying drawing, and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is an elevational view, partly insection, of the essential portion of an air circuit breaker embodyingthe present invention; Fig. 2 is an end viewof the circuit breakerstructure shown by Fig. l, and Fig. 3 is an enlargeddetail view of thearc interrupting structure.

' carried on a operating arm 6 that is secured to an insulating shaft 1for rotative movement therein and has a resilient connection at 6' withthe main operating arm for permitting limited overtravel or "wipe whenthe contacts are closed.

The arc-extinguishing structure or are chute 3 comprises in the presentinstance a pair of spaced insulating plates 8 composed of asbestos boardor the like forming an arc chamber that is adapted at its lower end toreceive the arc and to vent the are gases at the upper or exhaust end.The are chute is substantially closed at one side by the arcing horn Iand an insulating spacing and supporting member 9 secured to the supportor panel 4. and at the opposite side by the arcing horn 2'. Asillustrated, the arcing horn I forms part of the fixed contact structureand is secured in position by the terminal conductor 5. The arcing horn2 is secured between the insulating plates 8 by an insulating spacingmember 10. The arc chute so far described is of a more or lessconventional design, the arc formed between the contacts I and 2 beingblown by a magnetic field, for example, into .the arc chute along thearcing horns I and 2 so that the arc is greatly lengthened and cooled.

For the purpose of greatly increasing the interrupting capacity andefilciency of the arc chute, a compactly arranged group of spaced metalelements, such as copper pins H, are mounted between the plates 8 sothat the pins extend preferably in staggered rows as shown transverselyof the arc. As previously stated, the copper pins are preferably spacedfrom each other approximately 3 3" with respect to the adjacent arcingsurfaces of the pins. That is, the outer cylindrical surfaces of thepins are spaced approximately from each other throughout the arc chute.The theoretical reasons for this precise spacing are not believednecessary for a clear understanding of the invention' as it has beendefinitely proved that improved interrupting action takes place when thepins so spaced. It is of particular importance to note that this spacingis substantially independent of the magnitude of the current to beinterrupted and also of the exact number of plus within the chute,assuming, of course that there is sufiicient mass of metal within thechute "to dissipate the initial heat of the are so that the pins are notvaporized greatly. The spacing is also substantially independent of thevoltage impressed across the circuit breaker terminals, a ough it ouldbe understood that for high voltagm an ease ill size of the arc chutestructure is nose Under non" interrupting conditions the arc enters thechute along the arcing horns i and 2' and is split up as it moves amongthe pins so that extinction generally occurs well within the chute. Inthe case of heavy overloads or short circuits, the arc may be driventoward the exhaust or upper end of the chute. In such cases have foundthat spaced parallel insulating baffles 52 arranged to form a pluralityof narrow slots are effective to maintain the arc within the chute andalso to cause final extinction. The

- narrow slots, although very effective to prevent extension of the arcexteriorly of the arc chute, provide sufficient exhaust area openings topermit free venting of the arc gases formed within the chute.

As shown, the insulating bafiles 12 comprise a plurality of arcuatestrips of suitable arc resisting insulating material, such as asbestosboard or the like clamped between the upper edges of the plates 8 bymeans oi through bolts l3 and insulating spacers i4. tend throu hout thelength of the exhaust end of the chu e, The slots so formed arepreferably in width or less as I have found that a number of narrowslots having a sufllciently large aggrega e exhaust gas venting area aremost effective in maintaining the are within the chute and aiding areextinction. If desired, an integral moulded bafile structure can beused.

An air circuit breaker constructed as above described is compact in sizeas compared with air circuit breakers of similar rating having theconventional type of arc chutes. Furthermore, arc interruption is moreconsistent and the duration of arcing is considerably less.

The are can be driven into the arc chut y The bailles preferably exfromthe arcing horns.

conventional magnetic blow-out means, although in the present instance Ihave shown a magnetic structure associated with each of the contacts forinitiating movement of the are along the arcing horns into the chute.This magnetic structure comprises a pair of yokes I5 and I6 composed ofiron or other suitable magnetic material. The yokes are secured, asillustrated, to the contacts so that the open ends face each other in aposition offset with respect to the point of contact engagement so as tobe more remote That is, the iron yokes are mounted somewhat beneath thepoint of engagement between contacts i and 2 so that there will bepresent upon separation of the contacts a magnetic flux tending to drivethe arc into the arc chute. The arcing horn 2 and the movable contact 2are connected as in the usual case through flexible conductors i3 to theother terminal of the circuit breaker (not shown).

It has been found that in severe are interarrangement the ends of thepins seat within cylindrical recesses at i8, each cylindrical recessbeing countersunk as at [9 to form a conical recess so that the pins arespaced from that part of the wall insulation that is flush with theinner sides of the chute. This arrangement serves effectively to preventexcess fusing of the pin metal at the side walls of the chute. Analternate arrangement consists in turning down the ends of each pin acertain distance so as to increase the spacing between the pins wherethey are in contact with the side walls of the arc cnute.

It should be understood that my invention is not l mited to specificdetails of construction and arrangement thereof herein illustrated, andthat changes and modifications may occur to one skilled inthe artwithout departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electric circuit interrupter having arcforming means and an arcchute for receiving the arc comprising spaced insulating side walls anda compactly arranged group of metal pins mounted between said insulatingwalls transversely of the arc, the adjacent arcing surfaces of said pinsthroughout said chute being spaced substantially uniformly from eachother approximately 1%".

2. An electric air circuit interrupter having arc-forming means and anarc chute for receiving the arc comprising spaced insulating walls openat one end for venting the arc gases, a compact oup of metal pinsmounted within said chute between said walls in substantially uniformlyspaced relation to extend transversely of the arc path, the spacing ofsaid pins from each other at the arcing surfaces thereof beingapproximately and insulating baffle structure disposed beyond said pinsat the exhaust end of said chute, said baille structure forming aplurality of narrow slots not exceeding ,4," in width parallel to theare for confining said are within a d chute.

3. In an electric air circuit interrupter having arc-forming means, anarc chute comprising a pair of spaced insulating walls and a pluralityof metal pins mounted in said plates so as to extend between said walls,the ends of said pins being mounted within conical shape recesses insaid insulating Walls for minimizing fusing of the pin metal at saidwalls.

4. In an electric air circuit interrupter having arc-forming means, anarc chute comprising a pair of spaced insulating walls and a pluralityof metal pins mounted in said plates so as to extend between said walls,the ends of said pins "being mounted within enlarged recesses in saidinsulating walls whereby the insulation of said walls in flush alinementwith the inner sides of I said chute is spaced from said pins.

between said walls, the metal adjacent to the ends of said pins subjectto arcingbeing spaced with respect to the insulation surfaces of saidwalls for minimizing fusing of the pin metal at said walls.

JOSEPH W. SEAMAN.

